The invention relates to a nozzle for cutting steel workpieces and workpieces made of iron alloys, comprising a nozzle body with                an axial hole for the cutting oxygen and a pot-shaped, cylindrical free space at the outlet surface of the nozzle forming the cutting flame,        a plurality of heating oxygen holes and heating gas holes that are arranged in concentric circles around the axial hole, and        a hexagon head, if necessary, for screwing the nozzle onto a cutting torch.        
Oxygen-fuel gas cutting torches are intended to be used to cut steel workpieces and workpieces made of iron alloys. Blocks and slabs are effectively cut with that, for example. In so doing, the flame of the gas cutting torch ignited from a jet of oxygen and cutting gas is directed to the surface of the metal to be cut. The metal is heated to its ignition temperature because of that; a jet of cutting oxygen oxidizes the heating metal to bring about the cutting. In the process, the workpiece starts to burn and forms a gap that extends into a cut when the jet continues on. Since heat also arises while this takes place, this torch-cutting is called autogeneous, i.e. there is further preheating of the next steel layers of the area to be cut from the heat that is obtained from the burning steel.
A distinction is made in principle between premixed nozzles or postmixed nozzles or torches. In the case of premixing nozzles, heating oxygen and heating gas are mixed in the torch head before they flow out for ignition. In a postmixing cutting torch, the heating oxygen and the heating gas are discharged from the torch in an unmixed stream. The streams are mixed with one another via turbulence before ignition takes place.
So-called postmixed cutting nozzles for a cutting-torch unit in which there is an exclusive mixture of heating oxygen, heating gas and cutting oxygen at the outlet area of the flame are known from U.S. Pat. No. 6,277,323 B1 and CA 2,109,772 C. The nozzle is encompassed by a retaining nut that surrounds the nozzle and that is connected to the cutting torch. The nozzle has an axial hole for the outflow of cutting oxygen of a cutting torch. Furthermore, a plurality of heating gas holes are provided that are arranged in an internal, concentric circle around the axial hole. Moreover, the nozzle includes a plurality of heating oxygen holes that are arranged in an external concentric circle around the axial hole. Each of the holes, namely the axial hole, the heating gas holes and the heating oxygen holes, lead into outflow openings at an outflow end that transitions into a cylindrical free space in the retaining nut in which the cutting flame is formed.
This nozzle therefore involves an externally mixing—also called a “postmixing”—nozzle, i.e. there is no mixture of the gases inside the nozzle. Further, the nozzle has a multi-part design because of the additional retaining nut, so it is expensive and complicated to manufacture. On top of that, impurities such as cinder, dust and dirt particles can collect at the outlet area of the flame in the cylindrical free space in the retaining nut and penetrate into the nozzle.